Fri, 16 Sep 2011 19:15 UTC
Thousands saw it from Phoenix in Arizona to Las Vegas and Los Angeles and local authorities were swamped with reports of ball of flame in the night sky.
One witness said: 'It was huge. It had a green glow in front of it and a white tail. It looked like green fireworks going across the sky.'
But experts have revealed the phenomenon was most likely a fireball - a fragment of an asteroid that entered Earth's atmosphere.
The light was seen shooting quickly from west to east at around 7.45pm PDT, or 2.45am GMT.
Many reported it as bluish-green and others as yellow and orange. Some captured video of the object.
NASA scientist Don Yeomans, who runs the agency's Near-Earth Object Program, said: 'We can't say 100 per cent, but it's almost certain that the object was a fireball or very bright meteor the size of a basketball or baseball that likely disintegrated before it hit the ground.'
According to Mr Yeomans, the bluish-green colour suggests the object had some magnesium or nickel in it.
He added that orange is usually an indication it is entering earth's atmosphere at several miles per second, a moderate rate of speed.
'They make an impressive show for such a small object,' Mr Yeomans said.
Yeomans said fireball events are much more rare than shooting stars, but they happen on a weekly basis somewhere on Earth, usually over the ocean.
'It's a natural phenomenon and nothing to be concerned about.'
Astronomer Dennis Mammana, from Borrego Springs, said: 'Apparently this one put on a big show.
'The color of the object can tell you about the chemical composition of the meteor. The bluish-green color could mean it was nickel.'
At Maricopa County Sheriff's Office police fielded more than a dozen calls about sightings.
Sheriff's deputies at Deer Valley Airport in north Phoenix reported a sighting themselves, Lieutenant Justin Griffin said.
'It took an unusually long time to get across the sky,' Lt Griffin said. 'It's like a meteor. It's not like we had any flying objects with little green men or anything like that.'
Sergeant Steve Martos, of the Phoenix Police Department, said his agency received four calls 'regarding the light in the sky'.
He added: 'Myself and other officers observed it as well. We all made our wishes and went back to work. Nothing more to report. Have a safe night.'
The burning object also created a stir on Twitter.
One witness tweeted: 'I saw a lot of red in it from my vantage point in Phoenix, as well as the blue and green tail.
Another tweeted: 'It was crazy! Green and going fast & then it just burned out.'
Federal Aviation Administration spokesman Ian Gregor has confirmed there were no aircraft incidents reported in the Western region.